Many companies have a need to place telephone calls to their customers for various reasons. For example, airlines may need to notify passengers of changes in flight schedules, mortgage companies may need to notify customers of when payments are past due, and taxi companies may need to notify riders when a taxi will arrive later than expected. It can be very expensive, however, to have an agent of a company place a call, wait for the call to be answered, and then deliver the appropriate message. Many times a person does not answer the call; rather, an automated device such as an answering machine answers the call. In some situations, it may be acceptable to deliver a message to the answering party regardless of whether it is a person or an automated device. For example, when the telephone call relates to a delayed flight, it may be acceptable to deliver the message to either party. (Some automated devices simply provide a message or greeting and cannot record a message from the caller such as a message from a telephone company indicating that the called number is no longer in service.) In other situations, it may be desirable to deliver the message only to an answering machine or only to a person. For example, when the telephone call relates to a past due bill, it may be desirable to deliver the message only to the person and not to an answering machine. In general, it would be desirable to be able to detect whether a person or an automated device has answered a telephone call.
Companies can reduce the expense associated with placing such telephone calls by using automated dialer technology. Using such technology, telephone calls can be automatically placed by a call dialer and, when the dialer detects that a call has been answered, it can connect the telephone call to an agent who can deliver the message as appropriate. Various algorithms have been developed for call dialers that decide when and how many telephone calls to place. The goal of these algorithms is to reduce the cost per call and maintain a high level of customer satisfaction. These algorithms factor in the anticipated time to have a telephone call answered, the percentage of calls that will be answered by answering machines, the number of available agents, the average time for an agent to complete a call, and so on.
If a message should be delivered only to an answering machine or only to a person, then identifying the party (i.e., a person or an automated device) early in the telephone call can reduce the expense further. Various algorithms have been developed for analyzing the audio signal from the answering party to identify whether the party is a person or an automated device. For example, one algorithm monitors how long it takes for the answering party to start speaking on the assumption that a person generally starts speaking sooner than an answering machine. Another algorithm analyzes the pattern of silence and non-silence when a telephone call is answered to determine whether the pattern is similar to that of a typical automated greeting. Yet another algorithm applies speech-recognition technology to determine whether the words spoken when the telephone call is answered are typical of an automated greeting.
Unfortunately, these techniques for identifying the answering have met with limited success. In some instances, the algorithms have a high rate of misidentification. In other instances, it takes too long to identify the answering party. It would be desirable to have a technique that would accurately and rapidly identify the answering party as a person or an automated device.